Categories
Javascript

REST API with KoaJS and MongoDB (Part – 2)

In our last post about REST API with KoaJS and MongoDB, we got started with KoaJS and learned to create simple views. We also saw how we can access the query strings and incoming JSON payloads. In this tutorial, we are going to go ahead and implement the RESTful routes and CRUD operations with MongoDB.

In case you’re new to REST API development, you might also want to check out the REST API Concepts and our REST API Tutorials with Flask and Django REST Framework.

Installing MongoDB and NodeJS Driver

I am assuming you have installed MongoDB already on your system. You can install MongoDB using their official installer on Windows or Homebrew on OS X. On Linux systems, you can use the package manager that ships with your distro.

If you don’t have MongoDB installed locally, don’t worry, you can also use a free third party mongo hosting service like mLab.

Once we have MongoDB setup and available, we’re going to install the NodeJS driver for MongoDB next.

Connecting to MongoDB

We will create a separate file named mongo.js and put the following codes in it:

Our module exports just one function which takes the app object as the only parameter. Once called, the function connects to our mongodb instance and once connected, sets the people property on our app instance. The people property would actually be a reference to the people collection on our database. So whenever we will have access to the app instance, we will be just using the app.people property to access the collection from within our app. If the connection fails, we will have the error message printed on our terminal.

We have used promises instead of callback. Which makes the code a bit cleaner. Now in our index.js file, we will call the exported function like this:

That should import the function and invoke it. Assuming everything worked fine, you should see the message saying database connection established when you run the app next time.

Please Note: We didn’t create the mongodb database or the collection ourselves. MongoDB is smart enough to figure out that we used the names of non existing database / collection and create them for us. If anything with that name exists already, just uses them.

Inserting Records Manually

Before we can start writing our actual code, let’s connect to our mongo database and insert some entries manually so we can play with those data. You can use the command line tool or a mongodb GUI to do so. I will use the command line tool.

I inserted a document with my name and email address in the people collection of the polyglot_ninja db.

Implementing The Routes

Now we will go ahead and implement the routes needed for our REST API.

Please note: Too keep the actual code short, we will skip – validation, error handling and sending proper http status codes. But these are very important in real life and must be dealt with proper care. I repeat – these things are skipped intentionally in this tutorial but should never be skipped in a production app.

GET /people (List All)

This is going to be our root element for the people api. When someone makes a GET request to /people, we should send them a list of documents we have. Let’s do that.

Now if we run our app and visit the url, we shall see the document we created manually listed there.

POST /people (Create New)

Since we already have the body parser middleware installed, we can now easily accept JSON requests. We will assume that the user sends us properly valid data (in real life you must validate and sanitize) and we will directly insert the incoming JSON into our mongo collection.

You can POST JSON to the /people endpoint to try it.

Now go back to the all people list and see if your new requests are appearing there. If everything worked, they should be there 🙂

GET /people/:id (Get One)

To query by mongo IDs we can’t just use the string representation of the ID but we need to convert it to an ObjectID object first. So we will import ObjectID in our index.js file first:

The rest of the code will be simple and straightforward:

PUT /people/:id (Update One)

We usually use PUT when we want to replace the entire document. For single field updates, we prefer PATCH. In the following code example, we have used PUT but the code is also valid for a PATCH request since mongo’s updateOne can update as many fields as you wish. It can update just one field or the entire document. So it would work for both PUT and PATCH methods.

Here’s the code:

The updateOne method requires a query as a matching criteria to find the target document. If it finds the document, it will update the fields passed in an object (dictionary) in the second argument.

Delete /people/:id (Delete One)

Deleting one is very simple. The deleteOne method works just like the updateOne method we saw earlier. It takes the query to match a document and deletes it.

What’s Next?

In this tutorial, we saw how we can implement RESTful routes and use MongoDB CRUD operations. We have finally created a very basic REST APIs. But we didn’t validate or sanitize incoming data. We also didn’t use proper http status codes. Please go through different resources on the internet or our earlier REST API tutorials to learn more about those.

In our future tutorials, we shall be covering authentication, serving static files and file uploads.

Categories
Javascript

REST API with KoaJS and MongoDB (Part – 1)

We have previously written about REST API Development in length including tutorials using the Flask Framework and of course a multi part tutorial series using the Django REST Framework. In this tutorial series, we are going to focus more on JavaScript and see how we can build a very simple REST API using the KoaJS framework for NodeJS. We’re also going to use MongoDB and this no sql db list as our database.

Learning JavaScript

Before we can proceed, we should make sure that we’re proficient using JavaScript. We wouldn’t need any extra ordinary JS mastery but we need to have a certain level of command over JavaScript. If you are new to JavaScript and looking for some resources to learn the language, we have you covered. Please do checkout our JavaScript Learning Guide.

NodeJS and KoaJS

NodeJS has made JavaScript popular outside the browser world. There was a time, JS was meant to be used only on the browser side. For anything else, we would be using other languages like Java, Python, PHP etc. But then NodeJS came and proved that JavaScript is an equally viable language. With the very rapid growth of the platform, NodeJS today is being used for many types of programming and software development. From web backend and REST APIs to IoT tools and Desktop applications – NodeJS is literally everywhere.

There are many free and open source frameworks available for NodeJS but Express is perhaps the most popular option. Koa is quite like Express but it’s light weight, flexible and very simple. I personally am a big fan of this framework. At work, I have built multiple services on top of KoaJS and have been very happy with the outcome. This is why I chose Koa.

MongoDB

MongoDB has become very popular as a NoSQL database in the recent times. MongoDB is not like the traditional relational databases we’re so used to. Rather it’s a document oriented database where the documents look just like JSON. If you’re new to MongoDB, don’t worry, they have a brilliant University where you can take your courses free and master the database system. I have personally taken their courses and I would happily recommend the courses. They do cover some of the popular languages on the web. You will be learning to use MongoDB with Python / Java / NodeJS. Once you learn the concepts well, you should be able to transfer the knowledge to any other programming languages / platforms – so no worries if your favourite language is not available yet.

Getting Started

Before we can get started, make sure you have the latest NodeJS and npm installed. We would be using some of the modern JS syntax (ie. async / await), so please make sure you’re on the latest version of NodeJS (at the time of this writing, that would be Node 8). Please also make sure MongoDB is installed as well. On Windows you download the setup files and install them manually. On OS X, you can use a package manager like Homebrew. On Linux distros, you should be able to get them installed using the package manager available on your OS.

Creating The Project

Let’s first create a directory named “koa-example”.

Now we’re going to initialize the npm project.

The prompt will ask you a few questions. Once you complete answering them, we’ll be ready to start installing 3rd party dependencies.

Install KoaJS

Now we’re going to install KoaJS in our new project.

This should install KoaJS and save it as a project dependency in the package.json file.

A little more about Koa

Please note that Koa is being developed and maintained by the same people who work on Express. Koa is a much light weight version of Express except it follows a different path. Koa uses the modern JS features like async / await to make the code readable and maintainable. Although, in being light weight, Koa had to leave out many of the built in features in Express. Throughout our tutorial(s), we shall be installing third party packages, often to avail the same features which is prevalent in Express and other frameworks. Koa gives us a really minimal core and a very narrow, focused set of functionality. It lets us choose the components we need. That is in a way liberating and very flexible regardless of how inconvenient that might sound at the beginning.

One of the common Koa middleware I always install is koa-router which enables express like convenient routing on Koa.

Hello World!

Let’s start writing some codes, we shall of course start with the hello world example. We will first see the codes and then go through them.

The code is pretty straightforward. We are importing Koa and Router and creating new instances of them. We are then adding a new route / view to the router. Please note the usage of async functions. We mentioned earlier that Koa uses the latest JS features, notably the async and await features. If you are not familiar with the syntax, here’s a very in depth article that covers from the basics of promises, usages of generators and finally async and await. It would be a good read since Koa used to use generators to achieve similar results before async / await landed on Node.

The async function takes a parameter called ctx which is short for context. We can just set a body to the context and it will be rendered as response. If we pass certain types, for example a dictionary / object, it will be sent as JSON format. We can also access the request object using the context.

After the function is defined, we have used the routes middleware and launched the app on port 3000. If we browse the url http://localhost:3000 we should see the response we set.

Query Strings in KoaJS

Now that we have seen a basic hello world example, let’s see how we can access query strings in KoaJS. Query strings are appended to the url in the form – /hello?name=masnun – here the part starting from the question mark is the query string. We separate different parameters using & in the query string part. For example: name=masnun&country=bangladesh.

To access a parameter passed in the query string, we can use the ctx.request.query object to access the parsed querystring as JS object (dictionary). Let’s change our function to access the name from the query string and display a custom greeting.

Now visit – http://localhost:3000/?name=masnun and see how it works!

Accepting JSON

We have by now got used to the idea that we need to plug in 3rd party middlewares to achieve common tasks. One of the common thing in building REST APIs would be to accept JSON payloads. And like most other things, we need to use an external package to handle incoming JSON requests. In this case, we will use the koa-bodyparser package.

Now let’s modify the previous code to accept a POST request and parse incoming JSON so we can take the value for name variable from the JSON data. Here’s our modified code, first take a look and then we will discuss what we did different here:

The highlighted lines have been changed in this version. First we required the body parser package. Next we used it as a middleware. And finally, we accessed the value of name from the ctx.request.body object. Note, for query string it was request.query and now it’s request.body. The body parser parses the body of the request and sets the value there.

We can try our new code using the following request:

(The cURL command line was generated by Postman, feel free to use your favorite GUI tool for testing the APIs)

Logging Requests on Console

Our current app doesn’t list the requests it serves on the console. If we could get a nice log of what requests are being accepted and handled, it would help us with the workflow. We will be using the koa-logger package for just that.

Now we can use it in our app:

Now launch the app and make a few requests, you will notice nicely formatted output on your terminal.

Use Nodemon for Auto Reload

During development, it can be a tedious task to restart the app from time to time whenever you make some new changes. Nodemon is one of the tools which offer help with that. Install it globally and then just use nodemon . inside your current working directory. It will monitor file changes and restart the app as needed.

Learn more about Nodemon here – https://nodemon.io/ (along with installation instructions and use cases).

Up Next!

In this tutorial, we just got started using KoaJS and Koa Router package to build our views. In the next tutorial we shall resume our journey forward, learning to use MongoDB as our database.

Categories
Javascript

Learning JavaScript

You really don’t have to check where JavaScript stands in the TIOBE index, it is undoubtedly the most popular programming language in today’s world. JavaScript started big in the browser land but with the inception and rise of NodeJS, it has come out of it’s browser context and now being used in all sorts of tools and toys. From modern progressive web apps to desktop apps, from command line tools to IoT – JavaScript is literally everywhere. The language has it’s quirks, it’s not perfect and it gets a lot hatred from time to time. Despite the backlash, JavaScript continues to grow and get more and more mind share. Specially if you’re interested in web development, sooner or later you would need some level of skills in the language. So in this blog post, I will go ahead and list some of the resources that can help beginners in the JS world.

Learning The Language

JavaScript, the language can be used in the browser or on the server side through a framework like NodeJS. You can also use JS in different other places for scripting purposes. Depending on where we’re using the language, the libraries or the APIs can vary. But the language – it remains more or less the same. So before you want to start learning the next modern front end framework or the latest MVC framework in the Node land, you probably want to learn the language first. You should learn basics very well and have a solid grasp of the language before you choose your platform / stack.

  • Speaking JavaScript is an excellent book to get started with ES5. The same author brings you Exploring ES6.  And that’s not all, he also has another book – Exploring ES2016 and ES2017. You can probably already guess – the author, Dr. Axel Rauschmayer is pretty awesome. Reading these books will definitely get your basics strong. You can read these books free online.
  • Eloquent Javascript is also free online and should help you learn both the language and how it works in the browser.
  • JavaScript: The Good Parts is another excellent book. The book is not very big in terms of volume but it covers the language pretty well.
  • You Don’t Know JS is the title of a series of books written by Kyle Simpson. You can read the books free online. This series is pretty awesome!
  • JavaScript Allongé, the “Six” Edition – can also be read free online and packs lots of excellent content.

You may consult multiple books to understand the same topic. But it would be a good idea to start one book and stick to it.

Practising JavaScript

When reading through the concepts, please do try out the codes yourself. Just reading through won’t help much if you don’t practise. You can practise JavaScript in these places:

  • HackerRank – solve programming problems with JS here.
  • You can also train JS at CodeWars.
  • How about learning JS while playing some games? CodeCombat has you covered!
  • You can solve problems at Project Euler too!

What’s Next?

Once you have learned the language, you can choose to work on the front end or the backend or you can choose to be a full stack JS developer! The choice is yours. Do try both and see which ones you like. Having a solid understanding of the language will make it easier for you to pick up any stack / framework. So put extra focus on learning the concepts well and taking your JS skills to intermediate level!